Controlled shrinkage of photoresist

Abstract

A process for controlled shrinkage of photolithographic features formed in photoresist. A shrinkage profile is determined for the photoresist and sizes of the photolithographic features. The photoresist is then exposed to ultraviolet radiation and elevated temperature until the photolithographic features shrink a desired amount.

We claim: 
     
       1. A process for controlled shrinkage of previously defined lithographic features in a photoresist during photostabilization, said process comprising the steps of: determining a shrinkage profile for the exposed photoresist; and   exposing said photoresist features to ultraviolet radiation and elevated temperature of about 120° C. to about 230° C. until the photolithographic features shrink a desired amount, the shape of said features being preserved during said exposure.   
     
     
       2. The process according to claim 1, wherein said photoresist is chemically amplified. 
     
     
       3. The process according to claim 2, wherein said photoresist is coated on a semiconductor wafer and said photostabilization includes subjecting the wafer, coated with the chemically amplified resist, to UV radiation and simultaneously to a controlled ramped heating process to allow for a controlled shrinkage of the defined features. 
     
     
       4. The process according to claim 1, wherein said ultraviolet radiation has a wavelength of about 250 nm to about 350 nm. 
     
     
       5. The process according to claim 1, wherein said elevated temperature is from about 160° C. to about 230° C. 
     
     
       6. The process according to claim 1, wherein said elevated temperature is at least about 160° C. 
     
     
       7. The process according to claim 1, wherein prior to said exposure to ultraviolet radiation said photolithographic features have a minimum width of about 0.25 μm and after said exposure to ultraviolet radiation said photolithographic features have a minimum width of about 0.18 μm. 
     
     
       8. The process according to claim 1, wherein after said exposure to ultraviolet radiation said photolithographic features have a minimum width from about 5% to about 30% less than the minimum width of said photolithographic features prior to said exposure to ultraviolet radiation. 
     
     
       9. The process according to claim 1, wherein said photoresist is exposed to said ultraviolet radiation and said elevated temperature for a time of from about 20 seconds to about 220 seconds. 
     
     
       10. The process according to claim 1, wherein said photoresist is exposed to said ultraviolet radiation and said elevated temperature for a time of from about 30 seconds to about 140 seconds. 
     
     
       11. The process according to claim 1, wherein said photoresist is exposed to said ultraviolet radiation and said elevated temperature for a time of from about 70 seconds to about 140 seconds. 
     
     
       12. The process according to claim 1, wherein said ultraviolet radiation is deep ultraviolet radiation administered during the photostabilization process. 
     
     
       13. A method for forming a semiconductor chip device, said method comprising the steps of: carrying out a feature-forming exposure of photoresist on a surface of a semiconductor wafer;   subjecting said semiconductor wafer and said photoresist to a post exposure bake process;   subjecting said semiconductor wafer and said photoresist to a developing process, leaving features formed of said photoresist on said semiconductor wafer;   subjecting said semiconductor wafer and said photoresist to a photostabilization process, said photostabilization process resulting in shrinkage of said photolithographic features while preserving the shape of said features; and   processing said semiconductor wafer and said photoresist to form circuit features at least on the semiconductor wafer.   
     
     
       14. The method according to claim 13, wherein photostabilization process includes subjecting said photoresist to ultraviolet radiation and elevated temperature. 
     
     
       15. The method according to claim 14, wherein said ultraviolet radiation has a wavelength of about 250 nm to about 350 nm. 
     
     
       16. The method according to claim 14, wherein said elevated temperature is from about 120° C. to about 230° C. 
     
     
       17. The process according to claim 14, wherein said elevated temperature is from about 160° C. to about 230° C. 
     
     
       18. The method according to claim 14, wherein prior to said exposure to ultraviolet radiation said photolithographic features have a minimum width of about 0.25 μm and after said exposure to ultraviolet radiation said photolithographic features have a minimum width of about 0.19 μm. 
     
     
       19. The method according to claim 14, wherein after said exposure to ultraviolet radiation said photolithographic features have a minimum width from about 5% to about 30% less than the minimum width of said photolithographic features prior to said exposure to ultraviolet radiation. 
     
     
       20. The method according to claim 14, wherein said photoresist is chemically amplified, said photostabilization includes subjecting the wafer, coated with the chemically amplified resist, to UV radiation and simultaneously to a heating process including controlled ramped increased temperature, a constant set point increased temperature, or an increased temperature including a combination of at least one ramp and at least one plateau, thereby resulting in a controlled shrinkage of the defined features. 
     
     
       21. The process according to claim 14, wherein said photoresist is exposed to said ultraviolet radiation and said elevated temperature for a time of from about 20 seconds to about 220 seconds. 
     
     
       22. The process according to claim 14, wherein said photoresist is exposed to said ultraviolet radiation and said elevated temperature for a time of from about 30 seconds to about 140 seconds. 
     
     
       23. The process according to claim 14, wherein said photoresist is exposed to said ultraviolet radiation and said elevated temperature for a time of from about 70 seconds to about 140 seconds.